Computer Help/Advice.

I need a Desktop PC that is fast. I'm not looking for a gaming computer, I'm looking for a computer that can perform well. I don't mind getting separate parts for it as I can manage myself into building it. I preferably want a good cpu, good amount of ram, not a expensive graphics card, as i am not wanting to play games on it, and the rest (case,power supply, motherboard storage and optical drive) is for you to give me as i am not really sure in what to get.

My price range for this is from $400-$700. Preferably in the $500-$600 range, but more or less is fine.
Remember that i don't want it for games. So when stating what graphics card i should get, try and not make it a very expensive one.

Suggest!